Electric circuit breaker with novel flexible braid attachment



1966 D. B. POWELL 3,268,689

ELECTRIC CIRCUIT BREAKER WITH NOVEL FLEXIBLE BRAID ATTACHMENT INVENTOR. DA W0 5. POWELL A T TOR/V5) United States Patent 3,268,689 ELECTRIC CIRCUIT BREAKER WITH NOVEL FLEXIBLE BRAID ATTACHMENT David B. Powell, Bristol,Conn., assignor to General Electric Company, a corporation of New York Filed Oct. 22, 1964, Ser. No. 405,759 4 Claims. (Cl. 200116) My invention relates to electric circuit breakers, and more particularly to electric circuit breakers of the type including a pivotally supported contact arm carrying a movable contact which is connected to other circuit breaker components by a flexible conductor or braid.

Electric circuit breakers of the type described present a problem of avoiding breakage of the relatively fine strands of the flexible conductor or braid because of the repeated flexing thereof by motion of the contact arm between on and oil? positions. This problem becomes more severe the greater the angle of movement of the contact arm is, and with larger size flexible conductors. The problem is therefore greatly accentuated in so called compact circuit breaker designs, since the shortening of the length of the contact arm requires an increased angle of movement in order to achieve adequate contact opening distance, and since the increased ratings of such breakers require the use of relatively large flexible conductors. Since such breakers are required to pass endurance tests which call for the contact arm to undergo at least 10,000 operations, resulting in flexing of the flexible conductor or braid at least 20,000 times, breakage of the fine strands of the flexible conductors is quite likely to occur. Such breakage is especially likely to occur immediately adjacent the point where the flexible conductor or braid is attached to the contact arm, which is commonly done by brazing.

It is an object of the present invention to provide an electric circuit breaker including a pivotally supported contact arm which moves through a relatively large angle of movement and has a flexible conductor or braid connected thereto, the structure of the contact arm and the method of attaching the flexible conductor being such that the flexible conductor or braid is enable to withstand an extremely high number of mechanical operations without breakage.

It is a more specific object of the invention to provide an electric circuit breaker which includes a pivotally supported contact arm and a flexible conductor or braid connected thereto, the braid being connected to the contact arm in such a way as to prevent flexing closely adjacent the point of attachment of the braid to the contact arm, and also to provide a support around which the flexible conductor or braid is bent during extreme flexing, so that the conduct-or is not bent at an extremely sharp angle.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawing,

FIGURE 1 is a side elevation view of an electric circuit breaker incorporating the invention;

FIGURE 2 is a fragmentary side elevation view similar to FIGURE 1 but showing the parts in the off condition;

FIGURE 3 is a perspective view of the contact arm of the circuit breaker of FIGURE 1, and

FIGURE 4 is a perspective view of the contact arm of one form of the invention suited for use with higher capacity ratings.

Referring to FIGURE 1, the invention is shown as incorporated in an electric circuit breaker comprising a generally rectangular insulating casing including two generally tray-shaped casing halves which come together in a plane extending parallel to the side walls of the 3,268,689 Patented August 23, 1966 casing. In FIGURE 1, the casing half nearest the observer is omitted to show the parts.

The insulating casing 10 includes a stationary line terminal 11 of the plug-in type, adapted to make connection with a stab or blade type contact, not shown. A relatively stationary contact 12 is supported on the line terminal 11 and cooperates with a movable contact 13 carried by a contact arm 14. The contact arm 14, in turn, is connected by means of a flexible conductor or a braid 15 to the movable end of an elongated bimetallic strip 16, the-other end of which is rigidly attached to the inner end 17 of a conductor strap 18. The end 17 of the strap 18 is adjustably positioned by means of a calibrating screw 19 threadedly received in a nut 20 trapped in the insulating casing 10. The strap 18 is fixedly mounted in the insulating casing by suitable means such as by screw 21, and carries a load connecting terminal 22 at its outer end.

The bimetallic strip 16 carries a generally U-shaped magnetic field-piece 23 at an intermediate point which, when energized serves to attract a combined magnetic armature and latch member 24, carrying a latch projection 25, and including a return-bent end portion 26 extending around the movable end of the bimetallic strip 16. The armature-latch member 24 is biased toward latching position by means of a compression spring 27, acting on an extension 24A of the member 24, extending beyond its pivotal support 28 in the insulating casing 10.

The latch projection 25 serves to normally restrain the end portion 29 of a releasable support member 30 which is pivotally supported in the insulating casing such as by means of a pivot pin 31. i

The movable contact arm 14 is pivotally supported at 32 on an insulating handle member 33 which in turn is pivotally supported at 34 in the insulating casing. A tension type operating spring 35 has one end connected to the contact arm 14 adjacent its outer end, and its other end connected to an intermediate point of the releasable support member 30 at a hole 36. The motion of the contact arm 14 toward open circuit position is limited by its engagement with a raised boss or stop member 10A integral with the insulating casing 10.

For the purpose of assisting in the cooling and extinction of an are drawn between the contacts 12 and 13, a plurality of generally U-shaped flat metallic plates 38 are provided, which are slanted in the general direction of an arc venting passages 39.

In operation, rotation of the handle member 33 about its pivot 34 moves the pivotal support 32 of the contact arm 14 back and forth across the line of action of the tension spring 35, thus moving the contact arm 14 about the pivotal support 32 between an on position as indicated in FIGURE 1, and an 011 position as indicated in FIGURE 2. When the parts are in the closedcircuit or on position as shown in FIGURE 1, an excess current or overload condition causes the bimetallic strip 16 to warp so as to move the lower end thereof to the right as viewed, engaging the return-bent end 26 of the armature-latch member 24, and withdrawing the latch member 25 from the releasable support member 30. When this occurs, the action of the tension spring 35 rotates the member 30 clockwise about its pivotal support 31, moving the anchor point 36 of the spring 35 to the right as viewed and causing the line of action of the spring 35 to pass across the pivot point 32 of the contact arm 14 to automatically move the contact arm to an open-circuit position. Resetting of the breaker is accomplished by moving the handle 33 to its off position, causing the lower extension 33A of the handle to engage a pin 30A of the releasable support member 30 and rotating it in counterclockwise direction to relatched position.

In accordance with the invention, the movable contact arm 14 is designed to cooperate with the flexible conductor 15 in such a way as to minimize the flexing duty on the conductor 15, and to prevent flexing from occuring closely adjacent the anchor-point 15A of the braid. Accordingly, the movable contact arm 14, as shown particularly in FIGURE 3, comprises a bifurcated member in; cluding a contact supporting portion 14A and a pair of spaced-apart side portions 14B. The bight portion 14C of the contact member includes a hole 14D receiving the end of the operating spring 35, as shown particularly in FIGURES 1 and 2. Each of the opposed side portions 14B terminates in a rounded bearing portion 14E which is received in a corresponding notch 33B of the handle 33. In addition, each of the side portions 14B has a notch cut therein providing a rounded shoulder 14F. The conductive braid 15 is attached to one of the side portions 14B of the contact number 14 at 15A by suitable means, such as by brazing, at the front side thereof, just below one of the shoulders 14F, as clearly shown in FIGURES 1 and 2. Because of this arrangement, when the contact arm moves to the off position as shown in FIGURE 2, the flexible conductor or braid 15 is supported adjacent its point of brazing 15A to the contact arm 14. Thus substantially no flexing takes place closely adjacent the brazing point 14A, where breakage is otherwise most likely to occur. In addition, the conductor or braid 15 is supported by the shoulder 14F in the area in which bending does take place, thereby forcing the bend to be on a larger radius than would otherwise be the case, such, for example, as if the shoulder 14F were immediately adjacent the brazing point 15A, or if the conductive braid were attached to the back side rather than to the front side of the contact arm 14. (The term front side is used to refer to the side of the contact arm which is the same as that on which movable contact is carried.)

Circuit breakers constructed in accordance with the invention have shown an advantage over other ways of attaching a flexible conductor or braid by a factor of four to one so far as breakage is concerned. Thus, for example, circuit breakers constructed as illustrated have successfully passed endurance tests in which they were subjected to repeated on-off operations causing flexing of the conductor or braid more than 40,000 times, although other constructions tried in accordance with prior practice, experienced breakage at less than 10,000 flexures.

In the form of the invention illustrated in FIGURES 1 and 2, only a single conductive braid 15 is utilized to connect the contact arm 14 to the bimetallic strip 16.

In FIGURE 4 there is illustrated a form of the invention suited for higher current rated circuit breakers. In this case a pair of flexible conductive braids 115 is used to conduct the current from the contact arm 114. The operation of the invention in this form is substantially identical to that described in connection with FIGURES 1 and 2. It will be observed that both flexible conductive members 115 are protected from breakage by structure similar to that described in connection with FIGURES 1-3, including shoulder portions IMF.

While the invention has been shown in only two specific embodiments, it will be readily apparent that many modifications thereof may readily be made, and it is therefore intended that the attached claims shall cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising:

(a) an insulating casing,

(b) a relatively stationary contact mounted in said insulating casing,

(c) a contact arm pivotally supported in said insulating casing on a predetermined pivot support, said contact arm being movable between open and closed circuit positions and having a generally planar contact supporting portion,

(d) a movable contact mounted on one side of said contact supporting portion and movable thereby into and out of engagement with said relatively stationary contact,

(e) a relatively stationary conductive member mounted in said insulating casing at the side of said contact supporting portion of said contact arm opposite said one side,

(f) an elongated flexible conductor having one end thereof fixedly attached to said contact supporting portion of said contact arm and having its other end fixedly connected to said relatively stationary conductive member, said flexible conductor forming a bend between said ends when said contact arm is in said open-circuit position,

(g) said flexible conductor being attached to said contact arm at a predetermined point of attachment on said one side of said contact arm, said contact arm including a shoulder portion spaced away from said point of attachment of said flexible conductor, said shoulder portion being spaced from said movable contact in the direction of said pivot support, said flexible conductor extending around said shoulder portion, said shoulder portion of said contact arm being within the bend formed in said flexible conductor when said contact arm is in said open-circuit position, said shoulder preventing bending of said flexible conductor close to said point of attachment and limiting the sharpness of said bend of said flexible conductor.

2. An electric circuit breaker comprising:

(a) an insulating casing,

(b) a relatively stationary contact mounted in said insulating casing,

(c) an insulating handle pivotally supported in said insulating casing,

(d) a contact arm pivotally supported in said insulating casing on a predetermined pivot support and connected to said operating handle, said contact arm being movable between open and closed circuit positions and having a generally planar contact supporting portion, a movable contact mounted on one side 'of said contact supporting portion and movable thereby into and out of engagement with said relatively stationary contact,

(e) a releasable support member pivotally mounted in said insulating casing,

(f) current responsive latch means normally restraining said releasable support in operative position,

(g) an elongated tension type spring interconnecting said releasable support member and said contact arm, said handle member moving said pivot support of said contact arm back and forth across the line of action of said tension spring as said operating handle is moved between open and closed circuit positions,

(h) an elongated flexible conductor having one end thereof fixedly attached to said contact supporting portion of said contact arm at said one side thereof and having its other end fixedly connected to said current responsive means, said flexible conductor forming a bend between said ends when said contact arm is in said open circuit position,

(i) said contact arm including a shoulder portion spaced away from the point of attachment of said flexible conductor, said shoulder portion being spaced from said movable contact in the direction of said pivot support, said flexible conductor extending around said shoulder portion, said shoulder portion of said contact arm being within the bend formed in said flexible conductor when said contact arm is in said open-circuit position, said shoulder preventing bending of said flexible conductor close to said point of attachment and limiting the sharpness of said bend of said flexible conductor.

3. An electric circuit breaker comprising:

(a) an insulating casing,

(b) a relatively stationary contact mounted inside insulating casing,

(c) an elongated generally planar contact arm pivotally supported on a pivot support in said insulating casing at one end for rotation about an axis extending parallel to the major planar surface of said contact arm, and carrying a movable contact fixedly attached on one side of said contact arm at the other end thereof,

(d) operating mechanism mounted in said insulating casing and connected to said movablecontact arm, said operating mechanism including a manually engageable handle member movable between on and off positions to move said contact arm between open and closed circuit positions with a snap action,

(e) a relatively stationary conductive member mounted in said insulating casing at a point spaced away from said movable contact arm,

(f) a pair of elongated flexible conductors having a first end thereof fixedly attached to points of attachment on said one side of said contact arm and each having its other end fixedly attached to said stationary conductive member,

(g) said contact arm having a pair of shoulder portions, each of said shoulder portions being spaced away a short distance from one of said first points of attachment of said flexible conductors to said contact arm, said shoulder portions being spaced from said movable contact in the direction of said pivot support,

(h) said flexible conductors being bent over said shoulder portions respectively, whereby said shoulder portions prevent said conductors from flexing at a point closely adjacent said point of attachment to said contact arm and preventing sharp bending of said flexible conductors when said contact arm moves to opencircuit position.

4. An electric circuit breaker comprising:

(a) a generally rectangular insulating casing,

(b) a relatively stationary contact mounted in said insulating casing,

(c) a manually engageable handle pivotally supported in said insulating casing,

(d) an elongated generally planar contact arm, said contact arm being bifurcated at one end to form a pair of parallel arm portions, said arm portions ter- 5 minating in bearing portions having a pivotal en gagement with corresponding spaced apart portions of manually engageable handle,

(e) said contact arm having a movable contact fixedly attached to the end thereof opposite said bifurcated end on a first planar surface thereof,

(f) a latch member pivotally mounted in said insulating casing,

(g) a generally U-shaped releasable support member pivotally mounted in said insulating casing at one end thereof and having the other end thereof in releasably latched engagement with said latch member,

(h) an elongated tension type spring interconnecting said releasable support member and said contact arm whereby movement of said manually engageable handle member about its pivotal support moves the pivot of said contact arm across the line of action of said tension spring and moves said contact arm about its pivot point between open and closed circuit positions with a snap action,

(i) current responsive means mounted in said insulating casing and connected to said latch member to cause releasing movement of said latch member upon the occurrence of predetermined current conditions,

(j) a pair of elongated flexible conductive members each having one end thereof connected to said current responsive means and each having the other end thereof fixedly connected each to one of said arm portions of said contact arm, on said first planar surface thereof, said arm portions of said contact arm each having -a shoulder portion engaging said flexible conductive member at a point spaced from the point of attachment of said conductive member to said contact arm said shoulders being spaced from said movable contact member in the direction of said pivot support of said contact arm, whereby said shoulders prevent said flexible conductive members from flexing at a point closely adjacent to said points of attachment, and whereby said shoulders prevent said flexible conductive members from bending at too sharp a bend.

References Cited by the Examiner UNITED STATES PATENTS 2,318,085 5/1943 Leonard 200-116 3,081,386 3/1963 Koening et al ZOO--88 3,880,008 4/ 1963 Gelzheiser 2001l6 BERNARD A. GILHEANY, Prima'ry Examiner.

H. B. GILSON, Assistant Examiner. 

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING: (A) AN INSULATING CASING, (B) A RELATIVELY STATIONARY CONTACT MOUNTED IN SAID INSULATING CASING, (C) A CONTACT ARM PIVOTALLY SUPPORTED IN SAID INSULATING CASING ON A PREDETERMINED PIVOT SUPPORT, SAID CONTACT ARM BEING MOVABLE BETWEEN OPEN AND CLOSED CIRCUIT POSITIONS AND HAVING A GENERALLY PLANAR CONTACT SUPPORTING PORTION, (D) A MOVABLE CONTACT MOUNTED ON ONE SIDE OF SAID CONTACT SUPPORTING PORTION AND MOVABLE THEREBY INTO AND OUT OF ENGAGEMENT WITH SAID RELATIVELY STATIONARY CONTACT, (E) A RELATIVELY STATIONARY CONDUCTIVE MEMBER MOUNTED IN SAID INSULATING CASING AT THE SIDE OF SAID CONTACT SUPPORTING PORTION OF SAID CONTACT ARM OPPOSITE SAID ONE SIDE, (F) AN ELONGATED FLEXIBLE CONDUCTOR HAVING ONE END THEREOF FIXEDLY ATTACHED TO SAID CONTACT SUPPORTING PORTION OF SAID CONTACT ARM AND HAVING ITS OTHER END FIXEDLY CONNECTED TO SAID RELATIVELY STATIONARY CONDUCTIVE MEMBER, SAID FLEXIBLE CONDUCTOR FORMING A BEND BETWEEN SAID ENDS WHEN SAID CONTACT ARM IS IN SAID OPEN-CIRCUIT POSITION, (G) SAID FLEXIBLE CONDUCTOR BEING ATTACHED TO SAID CONTACT ARM AT A PREDETERMINED POINT OF ATTACHMENT ON SAID ONE SIDE OF SAID CONTACT ARM, SAID CONTACT ARM INCLUDING A SHOULDER PORTION SPACED AWAY FROM SAID POINT OF ATTACHMENT OF SAID FLEXIBLE CONDUCTOR, SAID SHOULDER PORTION BEING SPACED FROM SAID MOVABLE CONTACT IN THE DIRECTION OF SAID PIVOT SUPPORT, SAID FLEXIBLE CONDUCTOR EXTENDING AROUND SAID SHOULDER PORTION, SAID SHOULDER PORTION OF SAID CONTACT ARM BEING WITHIN THE BEND FORMED IN SAID FLEXIBLE CONDUCTOR WHEN SAID CONTACT ARM IS IN SAID OPEN-CIRCUIT POSITION, SAID SHOULDER PREVENTING BENDING OF SAID FLEXIBLE CONDUCTOR CLOSE TO SAID POINT TO ATTACHMENT AND LIMITING THE SHARPNESS OF SAID BEND OF SAID FLEXIBLE CONDUCTOR. 